001/*
002 * PermissionsEx
003 * Copyright (C) zml and PermissionsEx contributors
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 *    http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package ca.stellardrift.permissionsex.util;
018
019import org.immutables.value.Value;
020
021/**
022 * Represents a change in the value of some object.
023 *
024 * @param <T> the type of object being changed
025 * @since 2.0.0
026 */
027@Value.Immutable(builder = false)
028public interface Change<T> {
029
030    static <T> Change<T> of(final T old, final T current) {
031        return new ChangeImpl<>(old, current);
032    }
033
034    /**
035     * The previous value before the operation.
036     *
037     * @return the previous value
038     * @since 2.0.0
039     */
040    @Value.Parameter
041    T old();
042
043    /**
044     * The current value.
045     *
046     * @return the current value
047     * @since 2.0.0
048     */
049    @Value.Parameter
050    T current();
051
052    /**
053     * Get whether any change actually occurred.
054     *
055     * @return if a change occurred
056     * @since 2.0.0
057     */
058    default boolean changed() {
059        return old() != current();
060    }
061}